[18.0][FIX] contract: show smart buttons when partner has contracts

[shamnaskoyani]

Summary

• The Sale Contracts and Purchase Contracts smart buttons on the partner form were hidden whenever customer_rank == 0 / supplier_rank == 0. Partners created outside the Sales / Purchase flows (e.g. via the Contacts module) keep those ranks at 0, so users could not reach existing contracts from the partner form.
• Extended the invisible expression on each button to also consider sale_contract_count / purchase_contract_count (which are already rendered by the statinfo widget on the button). A button now shows whenever the partner has contracts of that type, regardless of rank. No change in behaviour when the rank is non-zero.

Test plan

• Install contract on a clean 18.0 database.
• Create a contact from the Contacts module (do not create any sale order / vendor bill for them, so customer_rank and supplier_rank stay at 0).
• Create a sale contract for that contact → open the partner form → the Sale Contracts smart button is visible with count 1; the Purchase Contracts button stays hidden.
• Create a purchase contract for the same contact → both smart buttons are now visible with count 1.
• Verify a contact with rank 0 and no contracts still shows neither button (no regression).
• Added unit test test_smart_button_visible_on_rank_zero_partner in contract/tests/test_contract.py.

Module maturity

• Production/Stable

Closes #1412

[shamnaskoyani]

CI is red on a pre-existing flake unrelated to this PR. Summary from the failed run:

• Tests themselves: 0 failed, 0 error(s) of 282 tests — all pass, including the new test_smart_button_visible_on_rank_zero_partner.
• The failure trigger is checklog-odoo picking up a WARNING ... TestContractPortal.test_tour: Killing chrome descendants-or-self of 341: 5 remaining followed by 5 leaked chrome (zombie) processes.
• test_tour is an HttpCase in contract/tests/test_portal.py that drives headless Chrome through contract_portal_tour. This PR does not touch the portal, the tour, or any HTTP test — only contract/views/res_partner_view.xml (admin smart-button visibility) and a unit test in contract/tests/test_contract.py.
• The chrome-zombie warning is a known intermittent issue with headless Chrome in Odoo CI; it does not indicate a real test failure.

Could a maintainer please re-run the failed jobs? I don't have rerun permissions on OCA.

[carlosdauden]

Related with:
#1413

[flotho]

easy code review
LGTM

[pedrobaeza]

This tests is useless, so please remove it.

[shamnaskoyani]

Thanks for the review @pedrobaeza — removed the test in fa54560. You're right, it was just asserting on the literal XML I had just written; the existing test_contract_count already covers count computation, and the visibility behaviour is purely a view-arch concern that doesn't add value as a Python test.

[pedrobaeza]

Please squash the commits into one. We don't want history that doesn't add value.

[shamnaskoyani]

Done — squashed into a single commit (ffee8f2). Thanks @pedrobaeza.

[pedrobaeza]

Reviewing the content, this avoids the direct creation of a contract for the partners. Isn't that what you was against in #1413 (comment), @carlosdauden ?